1. Field of the Invention
The present invention relates to a flat panel display and, more particularly, to an organic electroluminescent display and method for fabricating the same.
2. Description of the Related Art
An organic electroluminescent display (hereinafter referred to as an OLED) is an emissive display that electrically excites fluorescent organic compounds to emit light. An OLED may be classified as a passive-matrix type or an active-matrix type depending on what method is used to drive a matrix of N×M pixels (where, N and M are integers). An active matrix OLED consumes less power than the passive matrix type and has a higher resolution. Thus, it is used for display devices having a large viewing area.
FIG. 1 shows a plan view of a unit pixel region used in a conventional active matrix OLED.
Referring to FIG. 1, a scan line 125 is formed on a substrate and oriented in one direction. A data line 135 and a parallel common power line 131 cross the scan line 125. Both the data line 135 and the common power line 131 are insulated from the scan line 125.
Each unit pixel region includes a switching TFT (thin film transistor) 140 for switching a data signal applied to the data line 135 in response to a signal applied to the scan line 125, a capacitor 145 for maintaining the data signal applied through the switching TFT 140 for a predetermined period, and a pixel driving TFT 150 for allowing current to flow to a pixel electrode 170 by means of the data signal applied through the switching TFT 140. An emission layer (not shown) is formed on the pixel electrode 170, and an opposite electrode (not shown) is formed on the emission layer. As a result, an organic light emitting diode is formed to have the pixel electrode 170, the emission layer and the opposite electrode.
FIG. 2 shows a cross-sectional view illustrating a conventional method for fabricating the OLED taken along the line 1-1 of FIG. 1.
Referring to FIG. 2, a buffer layer 105 is formed on a substrate 100. A semiconductor layer 110 is formed on the buffer layer 105 using a first mask. A gate insulating layer 115 is formed on an entire surface of the substrate where the semiconductor layer 110 is already formed, and a gate electrode 120 is formed on the gate insulating layer 115 using a second mask.
Next, an interlayer 125 is formed on the entire surface of the substrate where the gate electrode 120 is already formed, and source/drain contact holes 125a are formed within the interlayer 125 to expose both ends of the semiconductor layer 110 using a third mask. Source/drain electrodes 130a, a data line 135, and a common power line 131 are then formed on the interlayer 125 using a fourth mask. The source/drain electrodes 130a are connected to the both ends of the semiconductor layer 110 through the source/drain contact holes 125a, respectively.
A via hole insulating layer 160 is formed on the entire surface including the source/drain electrodes 130a, and a via hole 160a is formed within the via hole insulating layer 160 to expose one of the source/drain electrodes 130a using a fifth mask. A pixel electrode 170 may then be formed on the via hole insulating layer 160 using a sixth mask. The pixel electrode 170 is connected to the source/drain electrode 130a exposed through the via hole 160a. A pixel defining layer 175 may then be formed to cover the pixel electrode 170, and an opening 175a is formed within the pixel defining layer 175 to expose the pixel electrode 170 using a seventh mask.
An organic emission layer 200 may then be formed on the entire surface of the substrate including the pixel electrode 170 exposed within the opening 175a, and an opposite electrode 220 is formed on the organic emission layer 200, so that the OLED is fabricated.
Thus, seven masks are required to fabricate the OLED in accordance with the prior art. Additionally, processes of forming a via hole 160a for connecting the pixel electrode 170 to the source/drain electrode 130a and forming a via hole insulating layer 160 are required. Such complicated processes increase the cost for fabricating the mask and the cost of production.